{"id":"BIT-jupyterhub-2026-54338","summary":"JupyterHub: Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","details":"JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. Prior to 5.5.0, invalid input to form-based login authenticators can place an unbounded attacker-controlled username in failed-login logs, allowing an unauthenticated attacker to consume logging and storage resources. This issue is fixed in version 5.5.0.","aliases":["CVE-2026-54338","GHSA-p43p-whwx-q52h","PYSEC-2026-3853"],"modified":"2026-09-29T10:10:59.725746688Z","published":"2026-09-29T08:44:40.894Z","database_specific":{"severity":"Medium","cpes":["cpe:2.3:a:jupyter:jupyterhub:*:*:*:*:*:python:*:*"]},"references":[{"type":"WEB","url":"https://github.com/jupyterhub/jupyterhub/commit/d6dc595f84b7509969686da31d87d6d69e7fce0a"},{"type":"WEB","url":"https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-p43p-whwx-q52h"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54338"}],"affected":[{"package":{"name":"jupyterhub","ecosystem":"Bitnami","purl":"pkg:bitnami/jupyterhub"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"5.5.0"}]}],"database_specific":{"source":"https://github.com/bitnami/vulndb/tree/main/data/jupyterhub/BIT-jupyterhub-2026-54338.json"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}],"schema_version":"1.9.0"}